>>10577124you definitely can. But my advise is not too. and don't paint the PCs (little rubber things that hold the joints))
in my case, I build MGs (ones that has internal frame to make it look more mechanically realistic)
I always paint the parts first, top coat the internal frame. for the armor, I paint the parts-gloss topcoat - apply the decals -apply satin coat, all before putting it together.
But you do you. some people enjoy just snap-building the kit, some enjoy doing some stuff like putting panel lining, color correcting with gundam markers and topcoating it, some enjoy fully painting the kit, some enjoy customizing their kits, some enjoy doing full monty, customizing and making dioramas with it. just do what floats your boat.